Physicochemical Properties Changes of Donuts During Vacuum Frying

Figures & data

Figure 1. Schematic diagram of vacuum frying system.

Table 1 Effects of IMC on frying time, volume and color changes, MC and FC of donuts fried under atmospheric pressure

Mix:water ratio (w:w)	IMC (%db)	FT (min)	ΔV (%)	ΔE	MC (%db)	FC (%db)
50:20	60.73 ± 0.67a	5	109.1 ± 5.6b	21.27 ± 1.04b	32.5 ± 1.2a	13.1 ± 1.3b
50:15	47.02 ± 0.79b	5	153.1 ± 6.5a	23.13 ± 0.21a	23.0 ± 3.1b	17.9 ± 1.3a
IMC = initial moisture content; FT = frying time; ΔV = volume change; ΔE = total color difference; MC = moisture content; FC = fat content; all determinations were on dry solid basis; all tests were performed in triplicate except volume change, which was performed in six replicates; means (± standard deviation) within a column followed by different letters are significantly different (P ≤ 0.05).

Figure 2. Moisture content versus frying time under atmospheric frying (50 + 20 means 50 g mix and 20 g water).

Figure 3. Oil uptake versus frying time under atmospheric frying (50 + 20 means 50 g mix and 20 g water).

Table 2 Effects of vacuum and temperature on frying time, volume and color changes, MC and FC of donuts fried under vacuum frying

P (kPa, vacuum)	T (°C)	FT (min)	ΔV (%)	ΔE	MC (% db)	FC (% db)
Atmospheric	190	5	109.1 ± 5.6f	21.3 ± 1.0a	32.5 ± 1.2b	13.1 ± 1.3g
3	150	8	176.9 ± 8.1c	14.6 ± 0.3d	35.3 ± 0.5a	24.7 ± 1.3cd
6	150	8	187.2 ± 6.9b	14.3 ± 0.9d	33.1 ± 0.5ab	29.2 ± 2.6b
9	150	8	208.0 ± 10.7a	13.8 ± 0.3d	32.4 ± 1.4b	35.8 ± 1.8a
3	165	7	165.8 ± 6.0d	16.7 ± 0.3c	34.1 ± 1.7ab	21.6 ± 2.0de
6	165	7	171.8 ± 6.5cd	16.3 ± 0.4c	32.3 ± 1.6b	25.7 ± 2.6c
9	165	7	179.8 ± 6.7bc	15.8 ± 0.4c	31.6 ± 0.7b	29.3 ± 2.6b
3	180	6	140.1 ± 7.1e	20.1 ± 0.9b	32.8 ± 1.6b	14.5 ± 1.8fg
6	180	6	145.0 ± 5.5e	19.6 ± 0.2b	32.5 ± 1.6b	17.6 ± 1.4f
9	180	6	148.0 ± 5.4e	19.2 ± 0.3b	32.1 ± 1.3b	21.0 ± 1.4e
P = vacuum, T = frying temperature, FT = frying time, ΔV = volume change, ΔE = total color difference, MC = moisture content, FC = fat content, all determinations are on dry solid basis; all tests were performed in triplicate except volume change, which was performed in six replicates; means (± standard deviation) within a column followed by different letters are significantly different (P ≤ 0.05).

Figure 4. Moisture content versus frying time during vacuum frying.

Figure 5. Oil uptake versus frying time at different levels of temperature.

Figure 6. Oil uptake versus frying time at different levels of vacuum.

Table 3 Textural profile analysis parameters of vacuum fried donuts using 2 cycles penetration test

Vacuum, kPa/ frying temperature, °C	Brittleness, N	Hardness-1, N	Hardness-2, N	Cohesiveness	Elasticity, mm	Gumminess, N	Chewiness, N.mm
Atm., high IMC	4.67A	1.10B	0.90B	0.18A	15.03A	0.20B	2.94B
Atm., low IMC	5.85A	2.45A	2.17A	0.17A	11.30B	0.42A	4.86A
3/150	1.88de	1.81c	1.42c	0.15bc	5.85c	0.27cd	1.59d
6/150	1.65ef	1.41d	0.95d	0.22a	5.34d	0.31bc	1.68d
9/150	1.43f	1.10e	0.95d	0.11c	3.34f	0.12e	0.39e
3/165	3.61b	2.85a	2.39a	0.20a	6.01c	0.56a	3.35a
6/165	2.82c	1.92bc	1.63bc	0.17ab	7.01b	0.33b	2.35c
9/165	2.02d	1.19e	1.05d	0.11c	3.67f	0.13e	0.49e
3/180	4.13a	1.58d	1.36c	0.15bc	7.68a	0.23d	1.77d
6/180	3.68b	2.13b	1.75b	0.16b	4.68e	0.34b	1.57d
9/180	2.94c	2.23b	1.77b	0.17ab	7.18b	0.39b	2.78b
Means within a column followed by different letters are significantly different (P ≤ 0.05).
IMC = initial moisture content.